Sainsbury's will become the first of four largest supermarkets in the UK to stop selling eggs from battery caged hens.

The supermarket will only sell eggs from un-caged birds, starting from February 5, following similar moves by Marks & Spencer, Waitrose and the Co-op.

Sainsbury's said more than 500,000 hens would no longer be kept in battery cages while 2.5-million fewer battery eggs would be sold each week in the UK.

Sainsbury's also aims to stop using caged eggs as ingredients in own-label food and drink by 2012.

The supermarket's move will have a huge impact, and will make animal welfare more mainstream, said Rowen West-Henzell, food business manager for Compassion in World Farming.

Under new EU legislation, conventional battery cages will be banned in 2012. Poultry farmers will be allowed to build larger ''enriched'' cages to give hens more space.